The invention relates to apparatus and a method of processing elastomeric materials. In particular, the process is directed to a means of producing carbon carbon bonds in a vulcanizable elastomer, and in particular, an elastomer that contains wire reinforcement.
Electron beam processing (EBP) is known in the art for treating elastomeric materials to enhance their green strength. EBP activates carbon atoms in a polymer and induces carbon carbon crosslinking. Carbon carbon cross linking in a green elastomer gives the elastomer added strength that makes it possible in some cases, and easier in other cases, to handle the green elastomer during processing before vulcanization.
Electron beam processing is known to induce an electromotive force in wire cords, along with a potentially high voltage, and for such reasons electron beam processing of wire reinforced elastomers has been generally avoided in the past.
In prior attempts to provide a means for using EBP on wire reinforced elastomers, a shunt was connected across the wire cords at the beginning of each windup roll. The shunt was then connected to plant ground potential at the windup.
On all fabric and wire calender lines, static build-up was removed with wire brushes, which require frequent replacement because of fast wear and lost contact with the sheet product.
Previous experiments have shown that the electric potential in a wire-reinforced elastomer that is subjected to EBP can be as high as 2,500 volts, with a very small current (in the milliamp (MA) range). This induced potential can damage an elastomer by arcing from wire to wire in the elastomer, thereby burning the rubber and also causing a safety hazard to the machine operator.
It is an object of this invention to provide an apparatus and method, which makes it possible to treat a wire, reinforced elastomer with electron beam processing.
It has been found, using the method of this invention, that static build-up that normally occurs when calendering elastomeric products can also be substantially eliminated.
Other objects of the invention will be apparent from the following description and claims.
A method of forming a reinforced composite 17 on a calender 11 comprises the steps of a) grounding guide rolls 19 that contact reinforcement 12 from a creel 18 prior to feeding the reinforcement 12 to a calender 11, b) coating the reinforcement 12 with rubber 23 while on the calender 11 to form a reinforced composite 17, and c) grounding rolls which contact the reinforced composite as the composite exits the calender 11.
The method in steps (a) and (c) may further comprise the steps of I) attaching slip rings 36 to rolls 14,15,19,21 which contact the reinforcement 12 and the composite 17 on the calender 11, and II) connecting the slip rings 36 to ground 27.
The method in step (a), comprising grounding reinforcement 12 from a creel 18, may further comprise the further steps of I) drilling and tapping the end of a roller shaft 32a to provide a threaded hole 37 for receipt of a bolt 39, II) threading a first end of bolt 39 into the threaded hole 37, III) attaching a slip ring 36 to a second end of the bolt 39, whereby the slip ring 36 rotates with the roll 32, IV) connecting a second bolt 38 to bearings within the slip ring 36 and attaching an electrical terminal 34 to the second bolt 38 whereby the terminal 34 remains stationary, and V) connecting the terminal 34 to ground 27.
In one embodiment, the method may comprise the further step of subjecting the reinforced composite to electron beam processing (EBP).
In further refinements of the method, the method may include the further step of placing at least one roll above the plane of the reinforced composite and at least one roll below the plane of the reinforced composite. Also, a further step of connecting bare wires to ground during calender changeover may be used.
In the illustrated embodiment, the method includes the step of subjecting a calendered sheet comprising rubber-coated wire to an electron beam of 2 to 14 mega-RADs.
In the illustrated embodiment, the slip ring 36 is provided as a mercury wetted slip ring.
Also provided is an apparatus 10 for grounding materials on a calender 11 which is used to coat wire reinforcement 12 with rubber 23, wherein the apparatus 10 comprises, a) at least one roll 14,15,19,21 for transporting material through a calender, b) at least one slip ring 36 connected to the roll whereby the slip ring 36 rotates with the roll while a terminal 34 attached to the slip ring stays substantially stationary while the roll rotates, and c) an electrical conductor 26 connecting each of the at least one slip ring 36 to ground 27. The apparatus 10 may further comprise d) an organizer roll 15 for directing wire through the calender 11, the roll having a first end of a conductive rod attached at one end thereof, and e) a slip ring 36 attached to a second end of the conductive rod 39.
In an illustrated embodiment, at least one roll is an organizer roll 15, and the conductive rod is a bolt 39 having a first end threaded into a threaded hole 37 in an end of the organizer roll. Also, a terminal 34 is connected to bolt 38 which is connected to bearings in slip ring 36.
The calender 11 includes apparatus 16 for applying a rubber coat on material passing through the calender 11. The apparatus 10 may include at least one grounding point on the calendered sheet 17 downstream of the calender 11, the at least one grounding point optimally comprising a guide roll 21 for the calendered sheet.
In the preferred embodiment, the apparatus further comprises an electron beam source 28 associated with the calender 11 down stream of a rubber coating apparatus 16 on the calender 11.